胎生期から幼児期における中耳骨間隙 : 中耳腔と骨髄腔との交通について [in Japanese] Marrow-Tympanum Connections in Fetuses and Infants [in Japanese]
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〔目的〕乳幼児の中耳粘膜下には骨間隙が存在し, 骨髄腔が中耳腔と交通する時期があるが, この特異な形態に関する報告は極めて少ない. 今回われわれは骨間隙に関し, 中耳腔内での存在部位, 間葉組織の有無について検討したので報告する.<br>〔対象および方法〕胎生20週から3歳までの29例58耳の側頭骨病理標本を評価の対象とした. 中耳腔内を13箇所に区分し, 骨髄腔と中耳腔が交通する骨間隙を, 間葉組織を介する型 (間葉型) と, 直接交通する型 (直接型) に分別し, 炎症耳と非炎症耳で比較した.<br>〔結果〕胎生20週から1歳2カ月まで交通する骨間隙が認められた. 部位では, 鼓室洞・顔面神経窩・乳突洞領域に多く見られた. 非炎症耳では乳児期に間葉型優位から直接型優位へと移行したが, 炎症耳では間葉型優位のままであった.<br>〔結論〕骨髄腔と中耳腔との交通は, 間葉型→直接型→骨間隙閉鎖と経過することが分かった. 骨間隙が閉鎖する1歳半ば頃までは, 中耳炎が骨髄腔に波及する危険性が示された. 骨間隙の多い部位として乳突洞, 鼓室洞, 顔面神経窩があり, 乳様突起炎や顔面神経麻痺に関与する可能性も示唆された.
The connections between hematopoietic bone marrow and the tympanum caused by bony dehiscences in immature middle ear were examined in 58 temporal bones of fetuses and infants. There were no anomalies in any of the cases, and they were divided into two groups: a group with inflammation of middle ear and a group without inflammation. The tympanic cavity was compartmentalized into thirteen portions to investigate the appearance of the connection, and the connections were classified into the mesenchymal type and the direct type dependent on residual mesenchyme in each portion. Marrow-tympanum connections were observed from 20 weeks of gestation until 14 months of age. In most cases the connections were the mesenchymal type. A large amount of mesenchyme remained in the inflammatory group. Some direct-type connections were observed in the non-inflammatory group from 1 month after birth onward and the mesenchyme was completely absorbed in these connections. Both types of the connections were frequently found in the antrum, facial recess and tympanic sinus. These results indicate that a marrow-tympanum connection is usually present in the temporal bone not only anomaly cases but also normal fetuses and infants. In addition, in normal cases without otitis media the connections first appear as mesenchymal type, and progress to direct type due to the absorption of mesenchyme. Presumably marrow-tympanum connections have structural disadvantage to induce osteomyelitis in cases with otitis media. And evoked osteomyelitis may cause complications such as acute mastoiditis and facial paralysis. The results of this study suggest that children under 2 years of age are at higher risk of complications of otitis media owing to marrow-tympanum connections than older children. Further study of the role of mesenchyme in otitis media is needed.
- Nippon Jibiinkoka Gakkai Kaiho
Nippon Jibiinkoka Gakkai Kaiho 111(1), 14-20, 2008-01-20
The Oto-Rhino-Laryngological Society of Japan, Inc.